P0340
Camshaft Position Sensor A Circuit Bank 1 or Single Sensor.
- Generic
- Powertrain
- Generic code
- High severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 3
- AreaIgnition system or misfire
- 40
- FaultThe specific fault in that area
What it means
P0340 means the engine control unit has detected a fault in the camshaft position sensor 'A' circuit on bank 1, or on the single sensor fitted to the engine. The control unit expects a valid, correctly timed signal from the sensor as the engine turns, and it set the code because the signal was missing, erratic or did not match the crankshaft position signal.
Symptoms
- Engine cranks but is slow to start or will not start
- Engine stalls unexpectedly or cuts out while driving
- Rough running, misfires or hesitation under load
- Reduced power, with the car possibly running in a limp-home mode
- Malfunction indicator lamp on
- Poor fuel economy or rough idle
Possible causes
- Faulty camshaft position sensorlikely
- Damaged, chafed or corroded wiring or connector in the sensor circuit (signal, supply or earth)likely
- Damaged or contaminated reluctor or target wheel, or a sensor with the wrong air gap or a loose mountingpossible
- Camshaft timing out of position due to a stretched or jumped timing chain or belt, or worn tensionerpossible
- Low or unstable system voltage, or a poor earth connection affecting the sensorpossible
- Oil leak or contamination getting into the sensor or connectorpossible
- Fault in the engine control unitrare
How to diagnose
- Read all stored and pending codes and the freeze frame data, noting engine speed, coolant temperature and whether the code is current or intermittent. Check for related crankshaft sensor or timing codes.
- Visually inspect the sensor, its connector and the wiring for damage, chafing, oil contamination, corrosion, loose fitting or heat damage.
- Check the battery condition and charging voltage, as low voltage can cause false signal faults.
- Check live data for camshaft and crankshaft signal presence and synchronisation while cranking and running. The exact parameters shown vary by model and engine.
- Test the sensor supply voltage, earth and signal wiring for continuity, shorts and resistance against the manufacturer's specification, as the sensor type (Hall effect or inductive) varies by engine.
- Inspect the sensor tip and the reluctor or target wheel for damage, debris or metal build-up, and check the sensor is seated correctly.
- View the signal on an oscilloscope and compare it with the crankshaft signal to confirm a good, correctly timed waveform.
- If the signals look out of step, check the cam timing against the manufacturer's procedure for chain or belt stretch or a jumped tooth.
How to fix
- Replace the camshaft position sensor if it fails testing, and make sure it is correctly seated and secured.
- Repair or replace damaged wiring and clean or renew corroded or oil-soaked connectors.
- Repair or replace a damaged reluctor or target wheel, or correct the sensor mounting and air gap where applicable.
- Correct the valve timing and replace worn timing components if the timing is found to be out.
- Repair charging or battery faults and poor earth connections that are causing unstable voltage.
- Fix the source of any oil leak that is contaminating the sensor or connector.
Can I keep driving?
High severity
Avoid driving if the engine stalls, runs roughly or is in limp-home mode, as a sudden loss of power can be unsafe. If the timing is suspected to be out, stop driving, since further running risks serious engine damage.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.